写程序用折线段逼近方式画如下平面曲线：

(1) ，(可以转化为显示表达式)

(2) ，(可以转化为显示表达式)

(3) , 。

注：用OpenGL的画线函数画线段；步长、窗口大小由大家自己确定；如果需要平移或放大缩小，可以直接对折线顶点的坐标值进行平移和缩放，也可以调用OpenGL的函数进行平移或缩放。

-Write a program segment with folded planar curve approximation method draw is as follows: (1), (which can be converted to show the expression)　(2), (which can be converted to show the expression)　(3),. Note: Draw a line function with the OpenGL-drawing line segments　step, the window size is determined by us ourselves　If you need to pan or zoom, you can directly on the polyline vertex coordinates to pan and zoom, you can also call the OpenGL functions to pan or scaling.